Skip to main content

9 posts tagged with "Nuclear Energy"

View All Tags

How Nuclear Fuel Fails

· 14 min read

The general public and even most nuclear engineers do not understand how easy it is for nuclear fuel to fail. Since the dawn of the nuclear era, nuclear fuels have been designed and built to meet only a small portion of the full requirements. This was due to material and technology limitations as well as costs. The only economical and practical way to use nuclear material for power has been simple fuel oxide pellets in metal cans.

That is now changing with the introduction of TRISO particle based fuels and use of advanced radiation tolerant ceramics. In this post, I will explain the performance goals of nuclear fuel and then show how normal fuels compare relative to TRISO based fuels.

Still there's a limit to what I can do with words. I can write all about nuclear accidents and the performance characteristics of traditional fuel compared to new TRISO-based fuels, but people often don't get it. The technical discussion of materials in nuclear reactors and how they affect fuel performance is not straightforward. But the practical differences between traditional and TRISO-based fuels would be plainly obvious if we could observe the fuel forms in action. We can't visually observe nuclear accidents as cameras can't survive the radiation, but we can show what happens using animations. So I rigged up a quick animation showing how traditional fuel and TRISO/FCM fuel look like as they encounter the same or similar conditions. I've made simplifications for the sake of comparison and illustration, but the general idea stands that during severe accidents, traditional fuel will fail to the point of melting and vaporization while TRISO/FCM fuel remains solid and functional.

Advanced Fission Reactors

· 12 min read

As a side-project, I collect and maintain information on upcoming nuclear energy extraction systems. Having it all in one place makes it useful for the public at large, policymakers, and scientists looking for a better understanding of the unfolding nuclear technology landscape.

There are now many designs, perhaps as many as 100 that are actively developed with more than a handful of people. To an outsider, these designs are all the same or arbitrarily different. Neither perception is true - there are important differences concerning cost and safety that should be more widely discussed.


· 3 min read

Nuclear Energy for Very Long Term Applications

We should build a nuclear powered monument that could last several thousand years. A reminder to future generations, human or not, that we existed and we thought of them. And I want it out in the open – not like that silly 1000-year clock buried in a hole in the middle of nowhere in Texas. More like the Pyramids or the great churches from our past. What should it be and how will it be powered?

Nuclear Powered Lighthouse Monument

The TRISO Fuel Revolution

· 15 min read

This is a TRISO particle from Ultra Safe Nuclear. The central sphere is a nuclear fuel like Uranium Carbon Oxide (UCO), and the shells are made of various ceramics.

Pebble Bed - The Nuclear Gumball Machine

· 21 min read

High temperature gas-cooled reactors (HTGR) come in basically two flavors: prismatic cores and pebble-bed cores. Both use graphite moderator and TRISO fuel particles to make the core which allows the reactor to reach high temperatures and handle accidents with relative ease. Both use helium to cool it, which allows thermal applications up to 950°C and power conversion efficiencies of 40%-55%, compared to just 300°C and 30% in water-cooled reactors. They differ in the geometry and form factor of the moderator and fuel which leads to significant differences in size, operations, and technology roadmaps.

In prismatic cores like the Ultra Safe MMR or Japan's HTTR, graphite is formed into chair sized hexagonal blocks with holes for cylindrical fuel pellets and separate holes for coolant channels. The core is maximally packed and nothing moves. Refueling the reactor involves swapping out the graphite blocks.

In Pebble Beds like China's HTR-PM or the very similar X-Energy Xe-100 design, the fuel and graphite are packaged as balls (called pebbles) that are poured into the reactor from the top and emptied at the bottom in a continuous fashion like a gumball machine.

Pebble Bed and Prismatic HTGR

Limits on the Cost of Nuclear Energy

· 16 min read

No - it's not "too cheap too meter." But it also shouldn't be prohibitively expensive to construct. Estimating nuclear energy costs compared to other energy generating assets is challenging and necessary to make financing decisions. We just have to be aware as to who has their fingers on the spreadsheet. Is it a wind and solar zealot, a fossil profiteer, or a nuclear startup? The following is a little exercise to see what the cost limits might be for nuclear energy.

Engineering and Economic Challenges of Fusion

· 38 min read

Fusion is generally touted by many as an energy "Holy Grail." Indeed, it appears to have similar qualities, being both perpetually elusive and miraculous, able to solve all mankind's problems. Media reporting tends to discuss the benefits of fusion with misleading and false statements and no discussion of fusion’s negative attributes. The financial and practical perspective of fusion based power is missing.